Not that long, if he's not trying all that hard. I'd guess...a couple minutes, tops. Basically, duration is dependent on how much effort Jeffrey expands to imprint any particular idea. Chances are he'll snap out of it pretty quick, since Jeffrey isn't attacking the Iskoort or paying that much attention. That, and while he might be on the gullible side, Truth Seeker isn't a human. While Jeffrey's powers seem to work on any sentient he meets (depending on their degree of resistance), they might not be as effective against non-humans. So....dealer's choice. : D